1. Field of the Invention
The present invention relates to an auxiliary gasline-heating unit. More particularly, the present invention relates to an auxiliary gasline-heating unit employed in a chemical vapor deposition apparatus.
2. Description of the Related Art
In a conventional chemical vapor deposition apparatus, gases, comprising a He (helium) carrier gas, a N.sub.2 (nitrogen) gas, a He-dilute gas, and a Ti[N(CH.sub.3).sub.2 ].sub.4 (TDMAT) vapor, are delivered by a gasline system comprising a TDMAT ampule 10, a He carrier gasline 12 connected to the TDMAT ampule 10, and a mixture gasline 14 connected to the TDMAT ampule shown as in FIG. 1. The mixture gasline 14 further comprises a N.sub.2 gasline 16 and a He-dilute gasline 18. The flow rate of the N.sub.2 gas and the He-dilute gas can be controlled by the mass flow controller 2 (MFC 2) and the mass flow controller 3 (MFC 3), respectively, and the flow rate of the He carrier gas can be controlled by the mass flow controller 1 (MFC1). Thus, the TDMAT vapor carried by the He carrier gas mixes with the N.sub.2 gas and the He-dilute gas through the gasline system after the He carrier gas passes through the TDMAT ampule 10.
However, in general, the exit temperature of the mixture of the N.sub.2 gas and the He-dilute gas is about 25.degree. C., and the temperature of the TDMAT vapor carried by the He carrier gas is about 50.degree. C.; thus, when the TDMAT vapor, the N.sub.2 gas and the He-dilute gas are mixed together, the temperature of the mixture is lowered from 50.degree. C. to about 32.degree. C. As a result, the TDMAT vapor is condensed in the vicinity of a valve PV 8. The condensed TDMAT can pollute the gasline system.